The inspiration for her novel was born during a long train journey.

was 是 be 动词的过去式，表示"是"或"存在"的状态。 born 是动词 bear 的过去分词形式，bear 本意是"生育、产生"，在这里 born 表示"诞生、产生"的意思。 was born 这个被动语态结构表示"被产生、诞生"，常用来比喻某事物的起源或产生过程。